If the corpus callosum is cut, a macaque trained to press a lever for electrical stimulation of striate cortex in one hemisphere responds immediately without further training if the "untrained" contralateral striate cortex is stimulated. Presence of the anterior commissure is required to establish this contralateral responsiveness in acallosal animals, but is not required at time of response. Thus the "engram" has passed to the contralateral hemisphere via the anterior commissure. The timing of this passage of the engram will now be studied, blocking conduction in the commissure by cooling at various times during the period of training. In the foveal area of striate cortex in unanesthetized squirrel monkeys 40% of the units are "luxotonic", i.e. their rate of discharge, sustained for minutes or hours is related to luminance of an unstructured visual field. The spectral characteristics (e.g. Purkinye shift?), prevalence of luxotonic units in areas representing peripheral visual fields, possible influence of eye movements or alterations of attentive state, are among the features to be examined in future experiments.